Method of producing tooth forms



Jan. 9, 1940.

I J. R. SCHWARTZ METHOD 0 F PRODUCING TOOTH FORMS V 1 I I I l r FiledMay 5, 1938 I Fig. 7 1m 8 Q FIN ISHFD man u FORM ATTORN INVENTO B R.SC'HW TZ Patented Jan; 9, 1940 l UNITED Foams Jacob K. Schwartz,Brooklyn, Y. Application May 5, 1938, Serial No .;20c,1s9*

2 Claimsf 1o]. 1s -.-'55. 1)

My .present invention relates to methods of n and means for, producing;tooth forms, and more particularly to ainovel method of,1and apparatus.

for, producing crown forms.

5 It may. be stated that one ofthe main objects of my presentinventionis to provide a method of producing crown forms of: a wide variety ofshapes and sizes; the method essentially com-v prising coating a toothmodelcomposed of a' substance easilyandquickly. soluble in a solvent,

which has no efiect on 'the coating material, a and subjecting thecoated model tothe solvent action when the coating is dry. 1

Another important f'object of a my' invention is" 16 to provide a methodof producing'dental crown" forms which includes the stepseof forming a,tooth crown model oi a, water-soluble composition'; coating. the modelsurface-wither waterinsoluble material; hardening-the coat; and fi-' 20nally placedthe coated model in a waterloath;

therebyflto dissolve completely the model while leaving ari'gid shellwhose form is exactly that:

of the model configuration. I 1 v Another object of the invention is toprovide ing placed intoa bath, after drying and baking;

' to provide a clean separation oi therigid, formed coat from each modelby a rapid dissolving of the model material. f}- l Other objects of my'inventionare toprovide dental model support-'jdviceS constructed posi-40 tively to retain a largenumber of models during the coating of thelattem the' support devices be ing additionally providedwith speciallydesigned' baking molds forjuse during the hardening stepl I 1 1fisiprovidedwith, a. V-shaped circular-groove 4 which-registers witha-male elementz'on the sup- 9 port device to provide 'DOSitiYGIBtBIItiOIl Of the of the present-process.g.;

Still other objects of my invention" are to improve generallythe'eiiiciency and speed of production of dental crown forms;andmore-espe cially to provide a method of producing cro-wnl forms whichis reliable and economical.

The novel featureswhich I believe to be char acteristic of myinvention'are setyforth inpar-i ticularity in the appendedclaimsptheinvention, itself, however, as to both itsorganizatiori andmethod of ,operation'will best beunderstood by".-

reference to "the following description taken in st0od"'tha;t in "outthis invention a com, 5 ,51

model, -Fig. 8*:is a central, longitudinal sectional view 5.1. of afinished crown" form after removal of the connection with; the drawingin: which I have indicated v.jdiagnammatically several constructionsl'bythe aid offwh'ich my. invention may be carried intoi'effect. Q i

In the drawing: 'Figs. land 2 showcentraL-ilongitudinal sec-,tion'al'flviews of alternate types of dental crown models adapted tqp inthe-processhaq d to my invention, ,7 v

.Fig; 3 is a plan-view of a portion of amodeI "10 support device 1adapted for use the type. sho-wninFig; 1

witli' models of 7 f1: isja transverse sectional view of the "supportshown in Fig; 3,! and taken 'along,, line' I d.t-4 looking the:direction of the arrows, v "Fig; 5is a transversesectional vie'wo'f a modi 1 --fied modelzsupportadapted foriuse' with models mg; 6 shoWsxthesupport device o'f Fig. 4 fitted inltransverse section, H

' :7 is acentraltlongitudi lal sectional view of a coatedmodel-just-priorto "removaloi the Referring nowto the accompanyingdrawing, I

'jwhereiri' like reference 'characters-in-th'e 'difiere en't :figures 1denote similar constructional ele- 30 ments,-there are'shown in Figs. 1,and 2 different types of crown models which can housed-"to "producecrown forms 'thereof. .Thniodel in Fig. 1- comprises two essentialsections; the sec tionsrare separated y afinished neck' line {whosefunction it is toidesignate the base ofgthe'crown formj after, the jcoating operation ,isijcompleted.

The section 2 above line I is' thetruemodel, or

' core,= whose contouris to beduplicated in the" forms; :The sectionsbelow lineI l' is a locking 0 base whose"function'it is tocooperatejwith'a ,Y-model support device to retain the mooeim positionduring" the coating operation. The-base ;3

model.

'Themodelin Fig 2gmechanic'allyediffersfrom thatin 1 in that the lockingbase3 is proof any'des'ired shape. Thus, itis to be under- ,with aspecial bakingmold,. both being shown plete set of crown models may bemolded to represent the crown contours of the upper and lower jaws, bothanterior and posterior. 'Such complete sets of models may beof the typeprovided with a locking base of the type shown in Fig. 1, or they mayhave the type of locking base shown in Fig. 2.

Those skilled in the dental art are fully aware of the manner of moldingtooth models such as shown in Figs. 1 and. 2. Each particular type ofcrown contour will have its set of"dies,,front and rear, to cast amodel. When constructing a set of dies to mold the type of model showngidity or configuration of the coating to be '30 quickly and completelysoluble inwater.

in Fig. l, the dies will be constructed to provide the groove 6 in thebase 3. Similarly in thecase of Fig. 2, each set of dies willbeconstructed to produce a bore 4 in the base 3 of the model.

It will'be obvious that the molding dies can be 1 arranged in a'widevariety of contours and sizes; these will depend upon the requirementsof the dental profession.

In molding the models it is desirable to "use for the com ositionthereof a material generally soluble in a solvent which will not affectthe ri.-

applied on the model. For example, when using a nitrocellulose solutionfor. coating the model, the latter is preferably composed of a substanceSuch a substance may be corn starch, potato starch or potato dextrine;or a mixture of plaster and any of the aforementioned substances may beused. Models composed of such materials are quickly soluble in hotwater, while theinitrocellulose coat is completely unaffected bythe-water- For the purposes of this method, however, theaforementionedmaterials are not the solematerials to be used. Ingeneral, as stated above, the material to be used for the model'willdepend upon the acfor production of contour-forms, the models are I Thelatter ,may

'tion of the solvent bath upon the model'coating; the essentialrequirementbeing that the coating be unaffected while'the model core isbein'g dissolved. Of course, any desiredtype of model solvent other thanwater may be used.

When a group of models have been "selected mounted in; a support device.comprise, as shown in Figs. 3 and 4, a pair of metallic sections 5 and twhich are mirror image duplicates "and; provide front and rear lockingsections for the bases of models. -While Fig. 3

shows only a single locking wellv 8, it will be understood that as manysimilar units as desired" may be employed. Asshown in- Fig. 4, andassumingthe type of locking base shown inFig. .1

is employed, each locking wellcorresponds in contour to a locking base3. Whena model base 3 is positioned between the sections 5-45, the basefits snugly in its well. Preferably, the neck line i will, be alignmentwith the top face 6 of. the 'support sections. A shallow basin 1 .isprovided in the upper face, ii to collect the small excessofcoatingsolution which may drip .frorn the model during the coatingstep, and

' lution of nitrocellulose.

locking well 9 of the type of support device adapted to position themodels with looking bases shown in Fig. 2. In this case the supportdevice is in one piece and a bore It is provided longitudinally throughthe successive wells 9. When the models are in position a rod (notshown) is run through the registered bores and bore Ill and locked inplace. In this way the models of Fig. 2 may be locked in position forcoating. Of course, any other type of lockingbase may be provided on atooth model; also, support devices may be provided with any desiredlocking means adapted to cooperate with such locking bases.

' Assuming, now, that the models of a desired type of tooth contour arelocked in position on a support device, the coating of the modelsections 2 is begun. Let it be further assumed that the models beingcoated are those having locking bases of the type shown in Fig. 1, whilethe contour sections are those of Fig. 2. The actual coating with thenitrocellulosesolution is. preceded by providing. on the exposed surfaceof each model a glazed surface. This. is done to close the pores of themodel-.material, and may be accomplished by. spraying the exposedsurfaces with a fine layer of shellac or gelatine. This glazing coatshould be of .amaterial which will not adhere. to the nitrocellulosecoating,.and

is, furthermore, water-'solubleso that it will subsequently wash outwith the modelmaterial.

, After the glazed surfaces are provided on the models, the latter aredipped-into an acetone 50- The consistency of the nitrocellulosesolution (which may be of any type readily purchased on the open market)is such as to coat the exposed surface of each model With.a layer ofuniform thickness. 'If desired,

the uniform coating canbe provided upon the models by spraying.In'actual usage the coating isextremely thin, and is of th'e order ofonefourth of-a millimeterin thickness. The nitrocellulose coats/on-themodels are permitted to dry and harden while still in thefsupportdevice. It will be appreciated that because of the common 'meunting forthe plurality of models, it is possi ble to'eliminate the many.manipulations it would require to operate on each model separately. Oncelocked in, a support device, a great many models are simultaneously.operated upon for the successive steps of the process.

The coatings on the models having driedand hardened, there is,associated with ;the support 'device a special baking mold shown in Fig.6.

In the latter there is shown only the relation be-.

tween'the specialjmold sections and the support I device sections. Thespecialmold may comprise complementary metallic sections i2 and Whenlocked together, and as shown in Fig; 6, the sections l?.i3 provide aplurality of mold units;

in each mold unit I4 is disposed a coated model.

Hence, each mold unit it has a configuration exactly correspondingto':-,that er the models to be subjected toheat. The. dotted line 15shows the space'occupiedby the uncoat'ed model; the space between lineH5 and the mold unit surface'is that occupied by thenitrocellulose'co'ating. Any desiredtype of adjustable clamping meanscan be used to secure the special mold device to the support device.5+6. 1 When the mold sections l2 iil have been'fittedin position andlocked together, the assembly is placed in any desired type of bakingoven. The nitrocellulose coats are subjected to dry: heat forfurtherhardening.

The sections i2+:l3 .are then-removed, and the contoursections of. themodelsshearedofi at the neck lines 1. During the heat treatment thesupport device.

becomes highly frangible, and is thereby more readily dissolved.

Fig. 7 shows the sheared, coated model; the

coating [6 is rigid and transparent. It conforms exactly to the contourof the crown form. Since the neck line of each model is positioned inalignment with upper face of the support device, any well known type ofslicing mechanism can be used to successively shear through the modelbodies along the plane of the upper face of the For example, apower-driven, rotatable, circular knife, of proper dimensions, can beemployed for this purpose. the periphery. of the base of the crown formis even, and will have no edge irregularities capable of harming the gumtissue since any excess coating material which may have accumulated onthe portion of the model within the basin 1 will necessarily be cut oiffrom the remainder of the coating when the model is sheared by theknife.

The sheared, coated models are now passed into a bath of water. It ispreferred to use water of a temperature suficiently high to dissolve themodel body in a rapid manner.- The finished crown form is shown in Fig.8; the model body has been removed without in any way affecting theconfiguration or rigidity of the coating I6. The aqueous solvent for themodel material has no efiect on the nitrocellulose; however, it doesdissolve the glazed surface on the model body. The separated crown formsmay now be collected from the bath and dried.

While I have indicated and described a method of, and means for,carrying my invention into efiect, it will be apparent to one skilledin. the art that my invention is by no means limited to the particularapparatus shown and described nor to In this way the sequence of stepsoutlined; many modifications may be madewithout departing from the scopeof my invention as set forth in the following claims. What I claim is: sV 1. In the art of producing dental crown forms, the method whichincludes molding from watertour section and a locking base, locking thebase to a support and exposing only'the contour section, coating thesurface of the exposed section with a layer of nitrocellulose whichbecomes rigid upon drying drying the layer of nitrocellulose, shearingthe coated contour section from said base at the support whereby thebase of the nitrocellulose layer is formed even and withoutirregularities, and dissolving the contour section away with water toeffect a separation of the rigid nitrocellulose coat.

layers on each surface to become rigid thereby to I provide said forms,shearing the coated contour sections away from the base sections at saidsupport whereby the base of each layer of nitrocellulose is formed evenand without irregularities, and

soluble material a tooth model which has a con- 7 subjecting the shearedcontour sections to hot JACOB R. SCHWARTZ.

